Wave generating system



Nov. 23, 1948. M. AR'rz'r 2,454,367

WAVE GENERATING SYSTEM Filed Nov. 29, 1944 if @Z 04552? Patented Nov. 23, 1943 WAVE GENERATING SYSTEM Maurice Artzt, Princeton, N. J., assignor to Radio Corporation o! America, a corporation oi' Dela- Wire Application November 29, 1944, Serial No. 565,737

The present invention generators. ,Y

The operation of certain electrical systems requires an energy wave of constant frequency which is periodically keyed on and off at a relatively low rate. When thesource of energy available is of a frequency lower than that required, a chopped energy wave of the above nature may be produced electronically by means of doubling circuits and keying tubes, but this introduces additional components which not only increase the complexity of the system but are'subiect to electrical or structural failure.

It has been proposed to generate such a periodically chopped Wave electro-mechanically by means of a tone generator the tone wheel lof which has a portion of itsteeth removed. While this proposal is satisfactory insofar as simplification of the system is concerned, it introduces an undesirable feature in that not only is the required tooth frequency obtained in the output, but in addition there is present a component representative of the unwanted chopping frequency.

The present invention overcomes the disadvantage attendant upon the utilization of an electro-mechanical device for producing a chopped energy wave by providing a method and means for substantially reducing the amplitude of the unwanted chopping frequency component in the output thereof. Moreover, not only is the amplitude of the unwanted chopping frequency component substantially reduced by means of the /present invention, but in addition the amplitude of the required tooth frequency is increased, thereby raising the ratio between the two to a point where the chopping frequency, component may be disregarded for most practical applications.

The principal object of the present invention, therefore, is the provisionof a method and means for producing electro-mechanically a chopped base wave having a high amplitude ratio of base frequency to chopping frequency.

A further object of the present invention is the provision of a method and means for producing, from a tone generator having a tone wheel with its teeth arranged in spaced-apart groups, an output in which the tone developed by the individual teeth on the wheel is relatively large in comparison with the tone developed by each group of teeth.

Other objects and advantages will be apparent from the following description of a preferred form of the invention and from the drawings, in which:

relates to i tone Fig. 1 is a partially schematicillustration of a r 7 Claims. (Cl. 171-252) preferred form of apparatus embodying the present invention; and

Fig. 2 is a set of curves illustrating the operation of the apparatus of Fig. 1.

In Fig. 1 is shown a tone generator including a tone wheel IS mounted for rotation on a shaft i2. Tone wheel l0 has on its periphery two similar groups of like teeth I4 and. I6, the teeth in these groups being evenly spaced, and with each tooth in one group diametrically opposed to the corresponding tooth in the other group. In practice a tone wheel having such a configuration may be produced by removing from the periphery of a conventional tone Wheel two diametricallyopposed sets of teeth, thus dividing the remaining teeth into two similar groups with equal spacing therebetween.

A pick-up device consisting of a magnet l@ having a coil 20 wound thereon is positioned adjacent the tone wheel lll in the usual manner, so that upon rotation of Wheel lli the magnetic field surrounding magnet i8 will be cut by passage therethrough of the teeth comprising groups I4 and i6. This produces in coil 2li voltage changes represented by the' composite waveform 22, curve (a) of Fig. 2, the wave portion illustrated being that produced by passage of either tooth group i4 or i6.

Composite wave 22 is made up of two component waves, one a substantially sinusoidal wave having the frequency and nominal amplitude of wave 22, -and indicative of the frequency of passage of the individual teeth of either group it or I6 past the magnet IB, and the other a substantially sinusoidal Wave 24 of lower frequency and lesser amplitude than wave 22,- and indicative of the frequency of passage of that particular group of teeth past the magnet i3. From the above it will be apparent that wave 22 departs from a substantially sinusoidal state by an amount equaito the instantaneous amplitude of wave 24. It is this wave 24 which is an undesirable factor in the output of the tone generator, and which the present invention provides a method and means for reducing by a substantial degree in a. manner to be described.

Referring again to Fig. 1, there is indicated by the reference character 25 a second magnet which is positioned similarly to magnet i8 in that its magnetic eld is cut by passage thereassess? the shaft i2, then the output of coil 2o would 1be 180 out of phase with the output oi` coil til.

By connecting the coils in series, the wave 2d would be cancelled out. However, such a procedurewould also cancel out the wave it.

By 'shifting the magnet 28 from such an opposed position to a new position which is offset therefrom by an amount equal to @/2, where c is the angle between the mid-points of adjacent teeth in either group, cancellation of wave 22 is avoided'. This is illustrated by curves (b) and ,(c) of FigpZ. Iln curve (h), the wave t@ produced 'in ,coil 26 `and corresponding to the wave 22 of curve (a) is inverted with respect to Wav'22 (denoting the assumed 180 out-of-phase relationship of the coils), and then shifted to the -right an amount equal to /2 (liig. l), or in other words by one half cycle of wave Sii. This causes the iii-phase peaks of Waves 22 and till, such as those indicated at 32 and i3d for example, to occur simultaneously, and the waves 22 and E@ accordingly add together so that the combined output of the coils 2@ and 2li appearing across the output conductors il@ (Fig. l) is of an increased amplitude as shown for example by the pealr te of wave il@ in curve (c).

As shown in Fig. 2, the wave G2 of curve (b) representative of the frequency of passage of one group of teeth past magnet 26, and corresponding to wave 2d of curve (a) is shifted only slightly from its assumed 180 out-of-phase relationship with wave 2d due to itsv lower frequency with respect to wave liti. As a consequence, waves 2d and it still cancel one another to a considerable degree, and the resultant wave lll of curve (c) will have a lower amplitude than either of waves 2d or il? alone. Thus the energy waves 22 and representing the tones respectively developed in the two coils d@ and il@ by the individual teeth on wheel iii. add together, while the waves 2d and d2, representing the tones respectively developed in the same two coils by the groups of teeth, oppose one another.

While two groups of like teeth have been shown, it will be clear that two additional groups ci like teeth, or any number of groups in multiples of two, may be employed as long as each tooth in. one group is diametrically opposed to the corresponding tooth in another group.

The two outer teeth in each group are preferably reduced from their original height shown by the brohen lines in Fig. l, thereby preventing sharp voltage changes in coils il@ and il@ when the groups enter or leave the vicinity of magnets is and 2G, and maintaining the sinusoidal character of the wave output in a manner which will be readily understood by those skilled in the art.

claim:

l. In a tone generator, a tone wheel having a plurality of diametrically-opposed teeth arranged in groups, a pair of magnetic pick-up devices positioned adjacent the periphery of said tone wheel and oifset from a diametricaliy-opposed relationship thereto, means for connecting said pick-up devices in series in an output circuit, means responsive to the passage of the individual teeth on said wheel when the latter is rotated to produce voltage changes in the said piclr-up devices which are in phase addition in the said outputcircuit, and means responsive to the passage of the said groups of teeth on said wheel to produce voltage changes in the said pick-up devices which are in phase opposition in the said' output circuit.

2. The combination according to claim i, in

which each of said pick-up devices comprises a magnet having a coil wound thereon, the said voltage changes being developed across said coils, and the said coils heini; series-connected in said output circuit.

3. In a tone generator, a tone Wheel having a plurality of diametrically-opposed like teeth arranged in groups, the teeth in each group having equal spacing therebetween, and a pair of pickup.. devices positioned adjacent the periphery of said tone wheel, said pick-up devices being oh'- set from a diametrically opposed relationship relative to the axis of said wheel by an amount equal to half the angle between corresponding points on adjacent teeth of any or said groups.

fi. The combination according to claim 3, further comprising means Vfor connecting together said pick-up devices, and means responsive to the rotation of said tone wheel for producing in the combined output of said connected pick-up of passage of said groups of teeth past said pick-- coil wound on said first magnet; a secondmagnet also arranged so that its held will be cut by passage oi said teeth, said magnets being so positioned that the largest of the angles formed thereby considered with respect to the anis oi rotation of said wheel is where 0 is the angle measured in degrees between the mid-points of adjacent teeth in either set; a coil wound on said second magnet; means for connecting the two coils; and means responsive to the rotation of said tone wheel for producing in each coil electrical waves indicative of the frequency of passage of the individual teeth of said sets through the respective magnetic helds of said magnets which will be in phase addition, while the electrical waves produced in each coil indicative of the frequency of passage of said sets oi teeth through the respective magnetic iields oi said magnets will bek substantially in phase opposition.

6. In an electrical generating system in which f there is developed a composite wave consisting of two component waves, one of which is both of a lower frequency and a lesser amplitude than the other component wave, the method of reducing the relative amplitude of said one component wave in the output of said system which comprises the steps of generating a second composite wave substantially identical in form with said firstmentioned composite wave and differing from a phase-reversed relationship with respect'thereto Iby an amount equal to approximately one-half the wave length of said other component wave, and combining said two composite Waves.

'7. In an. electrical generating system in which there is developed a composite wave consisting of two component waves, one oi which is of a lower frequency than the other component wave, the method of reducing the relative amplitude of said one component wave in the output of said composite waves.

MAURICE AR'IZT.

REFERENCES CITED The following references are oi' record in the' ille of this patent:

5 UNITED s'rs'msPATENTs Number Name Date 1,583,809 stoner my 11, 192s 1,597,453 Merrill Aus. 24, `192s 

